1. Field of the Invention
The present invention relates to a mobile object position detecting apparatus and method, and more particular to an apparatus and a method for warning of inability to detect a position due to faulty equipment.
2. Description of the Related Arts
Conventionally, there has been an emergency information device for detecting the current position of a vehicle and detecting the current positions of a navigation system for providing a guide to the destination so that the information about the occurrence of an accident, etc. and the position of the car can be transmitted in an emergency. In detecting the current position of the vehicle, a GPS device (Global Positioning System) has been widely used by a GPS receiver receiving and processing radio waves including the position information from a GPS satellite received by a GPS antenna of the GPS device, thereby detecting the current position.
However, the GPS antenna is normally provided in a position not easily checked by common users, and a ski carrier, a wiper, a metal film applied to the window of a vehicle, etc. in the reception area of the GPS antenna can disable radio waves to be received from the GPS satellite. Additionally, faulty connections to the GPS antenna and the GPS receiver or other faults can interrupt radio waves. In these cases, the current position a vehicle cannot be correctly measured. The following Patent Document 1 relates to an emergency information center apparatus, and designates the current vehicle location including the travel range, the angular range, and the initial error of the vehicle from the travel locus according to the position information about the final measurement position when the on-board device using the position data only about the GPS transmits emergency information and the GPS system cannot measure the position.
[Patent Document 1]
Japanese Patent Laid-Open Publication No. 2002-279594
However, in the vehicle position designating method disclosed by the above-mentioned Patent Document 1 , the current position cannot be correctly designated or the measuring process cannot be performed when abnormal reception of radio waves continues for a long time due to faulty equipment such as the interruption of the operation of the GPS antenna by any obstacles, a faulty connection or other faults of an antenna, etc.
Therefore, it is necessary to detect the presence/absence of receiving radio waves including position information, and warn a person in the vehicle of abnormal reception due to faulty equipment.
However, when a vehicle is traveling through a tunnel, in a mountainous area, among large buildings, etc., the radio waves from the GPS satellite often cannot be received due to geographic conditions which interrupt the GPS satellite and the GPS antenna. Therefore, if a warning is issued to a person in the vehicle only by detecting the presence/absence of receiving radio waves from the GPS satellite, then geographic conditions which may temporarily interrupt the radio waves can be reported as an incapability warning. This frequently bothers the person in the vehicle.
Therefore, the present invention aims to provide the mobile object position detecting apparatus for warning of abnormal reception due to faulty equipment without a warning for temporary incapable reception of position information due to geographic conditions.